Chandlery September 1, 1999 Issue

Harken Carbon Fiber Airblocks

The innovators in Pewaukee have done it again. Those who like high-tech, light and strong will be transported.

Harken has developed a new line of blocks. They’re called Black Magic Carbo Airblocks® and they’re outstanding in several ways.

(What we call ‘hollow’ blocks, which means any block without a spindle axle, were extensively reviewed in the November 15, 1994 issue, shortly after Harken introduced what it calls “Airblocks,” Frederiksen calls “Orbit Blocks,” Lewmar calls “Ocean Racing” and Garhauer calls “Lites.”)

Compared with comparable metal blocks, the new Harkens represent a 30% saving in weight and a remarkable 60% increase in strength—all thanks to Harken’s use of carbon fiber cheeks, plastic sheaves and Torlon bearings in fitted races. They’re UV-resistant and non-corrosive.

We didn’t attempt to test the stated strength. Harken says a 57 mm block has a safe working load of 800 lbs. and a breaking strength of 2,380 lbs. Equipped with 10 mm (7/16") line, like Spectra® or Technora®, they are powerful little blocks that make those of 20 years ago look somewhat antediluvian.

Currently available in 40 mm (about 1-1/2") and 57 mm (2-1/4") sizes, the blocks come in several interesting new variations.

We looked closely at one that had a tiny, concealed shift mechanism that lets the shackle head swivel freely or locks it either flat with or at 90° to the sheave. Other than having one block serve as a spare for several swiveling or fixed head blocks, we couldn’t think of a reason we might like to do that. But it’s interesting.

The other intriguing model is called a Ti-Lite™. Another step in the drive to eliminate weight, the Ti-Lite does away with the heavy head post and shackle and substitutes for them a lashing of Spectra line (see photo).

Because you do the lashing yourself (it comes with one meter of 3 mm Spectra), it can be made adaptable for a boom, a stanchion base, a bail—anything that can be encircled by loops in the lashing. It also can be cinched down very tight to make it stand up. Perhaps best of all, it will remain dead silent, no more clatter, and no wear.

It may require a bit of mental adjustment to trust three strands of Spectra as a replacement for a stainless shackle, but then it took a while before folks conceded that GPS is quicker and more accurate than a sextent.

Available in single swivel, swivel/becket, double swivel, double/becket, triple swivel, triple/becket and cheek block, the new Harken blocks didn’t make it into the 1999 discount catalogs. Perhaps it’s a good excuse to contact Harken and ask for their fine catalog. (Harken, 1251 E. Wisconsin Ave., Pewaukee, WI 53072-3797; 414/691-3320.

Beats Using Your Finger
Nigel Calder says it plainly in his respected book, Boatowner’s Mechanical and Electrical Manual, published by International Marine/McGraw-Hill (800/262-4729):

“Keep batteries topped up with distilled or clean fresh water. The battery’s internal plates are irreparably damaged by exposure to air. Maintain fluid levels one-quarter to one-half inch above the plates, but no higher. Overfilling will lead to spewing of electrolyte from the filler caps during charging.”

A new company in Texas offers a way to be fairly precise about heeding Calder’s advice.

The product is called Wet Check™. It’s just a bunch of cardboard fingers, the small ends of which have two marks printed at one-quarter and one-half inch. Break one off the card, stick it in a battery cell and read the level by how much of it gets wet. Throw away that finger and grab another for the next cell.

They are especially handy if you cannot get your head in a position to look down into the battery (as it is in our Tartan test boat), even with a flashlight, and are loath to stick a finger in the sulfuric acid.

Wet Checks come two cards (six fingers each card) to the $2.95 pack. (American Business Concepts, Inc., 4400 Sunbelt Dr., Addison, TX 75001, 800/877-4797, or take a look on

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